Class 17 — Friday October

You're so random

Like to look around — And see random acts of grace — By everyone

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Look both ways

• Back or ahead

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Agenda

• Introduce randomness using Python module random

• Continue with data set processing

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Download

• Program chosen.py

• Program pick_a_number.py

• Program bit_by_bit.py

• Program octane.py

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To do list

• Review class artifacts.

• Complete homework

• Check out random module

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Being random

• Python has a standard module random with extensive capabilities for generating pseudo-random values.

• Why say pseudo-random? Since we are using algorithm there is some determinism involved.

• There are algorithms that can generate values that appear to be so random that can fool everyone (at least for now).

• There are three random module functions of particular interest to us now.

• Function choice(): choose value from a string, list, set, or tuple

• Function seed(): specifically prime the random number generator

• Function randrange(): choose value from a range interval

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Program chosen.py

• Demonstrates some simple usage of random module function choice()

• Some program runs

Enter a string: abcdefghij

Four random characters from string abcdefghij : e a j d

Enter some words: th fo ju ov th la lo

Four random words from list ['th', 'fo', 'ju', 'ov', 'th', 'la', 'ol'] : ov lo la ov

Enter a string: abcdefghij

Four random characters from string abcdefghij : a i b h

Enter some words: th fo ju ov th la lo

Four random words from list ['th', 'fo', 'ju', 'ov', 'th', 'la', 'ol'] : th fo th ju

Enter a string: simultaneously

Four random characters from string simultaneously : i y m t

Enter some words: 31 41 597 2 71

Four random words from list ['31', '41', '597', '2', '71'] : 71 597 31 71

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Program pick_a_number.py

• Demonstrates some simple usage of random module function randrange()

• Some program runs

Enter four integers: 10 20 75 100

Four random values from interval [ 10, 20 ): 14 14 18 18

Four random values from interval [ 75, 100 ): 82 75 92 80

Enter two integers: 10 100

Four random values from interval [ 0, 10 ): 7 4 3 5

Four random values from interval [ 0, 100 ): 15 28 64 87

Enter four integers: 10 20 75 100

Four random values from interval [ 10 , 20 ): 11 11 19 15

Four random values from interval [ 75 , 100 ): 89 85 76 99

Enter two integers: 10 100

Four random values from interval [ 0, 10 ): 1 2 8 6

Four random values from interval [ 0, 100 ): 57 63 81 18

Enter two integers: 10 100

Four random values from interval [ 0, 10 ): 3 5 3 6

Four random values from interval [ 0, 100 ): 29 12 32 5

Enter four integers: 10 20 75 100

Four random values from interval [ 10 , 20 ): 13 14 16 19

Four random values from interval [ 75 , 100 ): 92 98 75 75

Enter four integers: 0 8 31 39

Four random values from interval [ 0 , 8 ): 7 2 1 3

Four random values from interval [ 31 , 39 ): 37 36 32 37

Enter two integers: 2 10

Four random values from interval [ 0, 2 ): 1 0 0 1

Four random values from interval [ 0, 10 ): 6 6 2 8

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Program bit_by_bit.py — generating random lists of values

• Generates a list of n bits (binary digits) for a user-supplied n.

• Some possible program runs

How many bits: 8

[1, 0, 0, 0, 0, 0, 1, 1]

How many bits: 8

[1, 0, 0, 1, 1, 0, 0, 1]

How many bits: 28

[0, 1, 0, 0, 1, 1, 1, 1, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 1, 1, 1, 0, 1, 1, 0, 1]

How many bits: 28

[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 1, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 1, 1]

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Program octane.py

• Prompts and gets three user-supplied integers s, n, and d. Uses integer s as a seed to the Python random number generator.

• Accumulates a list of n octal digits (base 8 digits; that is digits from the interval 0 to 7) one by one. Afterwards, prints the list of octal digits.

• Determines and prints the number of occurrences of d in the list of octals (check out the list module for a helpful function.

• Some possible program runs

Enter three numbers: 1112 12 1

octal digit list: [4, 1, 4, 0, 6, 1, 5, 2, 5, 1, 1, 2]

number of times value 1 in list: 4

Enter three numbers: 1112 12 5

octal digit list: [4, 1, 4, 0, 6, 1, 5, 2, 5, 1, 1, 2]

number of times value 5 in list: 2

Enter three numbers: 8 9 6

octal digit list: [3, 5, 6, 2, 3, 0, 1, 2, 3]

number of times value 6 in list: 1

Enter three numbers: 8 9 6

octal digit list: [3, 5, 6, 2, 3, 0, 1, 2, 3]

number of times value 3 in list: 3

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